Cutting stretched interplayer sheeting

ABSTRACT

This invention involves cutting a series of individual sheets of thermoplastic interlayer material into a selected trapezoidal shape of adjustable length and shape by winding a continuous ribbon of said material on an adjustable mandrel and cutting the continuous ribbon while mounted on the mandrel properly adjusted. The adjustable mandrel of this invention comprises means for independently adjusting the diameter or circumference of its opposite axial end portions so as to ensure that the plies of said material wound onto said mandrel are cut into trapezoidal shapes of the proper length and outline shape by one or more simple cuts parallel to the axis on which the mandrel is mounted for rotation.

This is a division of application Ser. No. 814,068, filed July 8, 1977.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to apparatus for cutting continuousribbons of flexible plastic material suitable for use as interlayermaterial in laminated automobile windshields into a series of discretesheets, each having a preselected trapezoidal shape. The presentinvention has particular use in the fabrication of interlayers having aband of dye disposed along one longitudinal edge margin of theinterlayer destined to be located along the upper edge of the laminatedwindshield when the latter is installed in an automobile.

Recent designs of automobile windshields require the lamination of bentglass sheet sthat are substantially trapezoidal in outline. The plasticinterlayers for such sheets are usually supplied in the form of acontinuous ribbon mounted on a roll. In the past, such ribbons have beencut into rectangular shapes by rotating the ribbon about a reel to formseveral layers or plies and cutting the layers transversely to form aseries of rectangular sheets whose length approximated the outerperimeter of the reel. A considerable amount of plastic has been lostthrough trimming two triangular-shaped portions from the opposite endsof the rectangular sheets to convert from rectangular to trapezoidalshapes. Furthermore, the majority of automobile windshields are providedwith a dyed upper portion. The purpose of this tinted or dyed portion isto serve as a means for avoiding glare and to reduce the intensity ofoverhead radiation entering into the vehicle and annoying the driver andhis passengers.

It is usually desirable that the colored strip portion extend along thetop portion of the windshield. The lower edge of the colored or tintedstrip should extend generally horizontally when the windshield isinstalled across the front of the automobile in an inclined position.Since the windshields of modern cars have a continuous curve from oneside to the other side, it is necessary to stretch the interlayer insuch a manner that the edge portion that is colored, tinted or dyed isstretched to a lesser extent than the undyed portion forming the lowerportion of the windshield when the latter is installed.

In the past, dyed plastic has been stretched differentially either onadjustable shaping frames or shaping cones. The shaping frames stretchone sheet at a time. The sheet must be mounted on the frame beforestretching and removed after stretching, a time-consuming operation.Shaping cones permit the winding of several layers, which are stretchedsimultaneously, or the continuous movement of a continuous ribbonthereacross. Both of these latter techniques are faster than theadjustable frame technique for stretching plastic differentially, but donot make it possible to cut individual interlayer sheets of the propersize (particularly length) and proper trapezoidal shape for more than asingle production pattern while the continuous ribbon is wound on thestretching cone in its differentially stretched condition.

2. Description of the Prior Art

U.S. Pat. No. 2,933,759 to Startzell discloses a plastic stretchingapparatus that resembles an umbrella for stretching partially dyedplastic differentially. The ribs of the umbrella extend peripherallyaround a center shaft so that the ribs of the umbrella are capable ofmoving in unison from a generally cylindrical shape to a conical shape.The Startzell patent discloses more than one embodiment. In one of theseembodiments, links of different lengths are provided on the oppositeaxial ends of the umbrella-like structure to expand the opposite axialends radially or circumferentially in different planes transverse to thecenter shaft simultaneously and at different rates. Thus, the Startzellstretching apparatus is capable of stretching sheets differentiallydepending upon the relative lengths of the links that pivotally connectsleeves mounted on the center shaft to each end of the ribs of theumbrella. The Startzell stretching umbrella is thus able to convert acontinuous ribbon of partly dyed or tinted plastic from a ribbon havinga rectangular shape into a ribbon having a curved border between thedyed and undyed portions of the plastic ribbon. The structure of thestretching umbrella has to be rebuilt or a different umbrella has to beprovided for each different pattern of windshields to be produced.

U.S. Pat. No. 3,467,332 to Bachman discloses a mandrel suitable forcutting an elongated ribbon of clear plastic into trapezoidal lengthsthat interfit with one another so that each two lengths of plastic thatare cut from each circumferential ply of the plastic sheeting interfits.Clear plastic sheeting does not have to be distorted in the mannerneeded for plastic having a dyed portion. While the plastic cuttingapparatus of the Bachman patent discloses means for adjusting the lengthof the periphery of the plastic layers or plies and provides means fororienting a pair of guides for cutting devices mounted on the cuttingreel, this appartus is incapable of use with partially dyed plasticexcept in the wasteful manner provided by prior art apparatus whichrequired the plastic to be cut to rectangular shapes and then thetriangles removed from the opposite longitudinal ends in order toprovide the trapezoidal shapes desired.

U.S. Pat. No. 3,969,186 to Stark et al discloses an adjustablestretching cone having an adjustment mechanism operated by a crank in astandard manner to change the diameter of the cone along its narrow end.A plastic ribbon wound about the cone is differentially stretched anamount that depends upon the relative circumference of the smaller endof the cone compared to its larger fixed end. After the continuousribbon is differentially stretched, it is cooled and cut to finitelengths. Each finite length has its lateral edges stretched to curvedconfigurations of different arc lengths. According to this apparatus,each length is cut individually from the continuous ribbon. The cuttingoperation may thus limit the rate at which the individual sheets orlengths of plastic are fabricated from the continuous ribbon. On theother hand, the distorting or differential stretching of the continuousribbon is performed while the conical stretching frame is rotated andthis provides a limited time to differentially stretch the plastic andpermit the plastic to be cooled throughout its thickness to atemperature at which it becomes permanently set in its deformed shaperesulting from the differential stretching of its opposite side edges.

Thus, prior to the present invention, the glass laminating art lacked amethod and apparatus that made it possible to cut a plurality ofindividual sheets of different sizes and trapezoidal shapes as neededfrom a single continuous ribbon of particularly dyed plastic.

SUMMARY OF THE INVENTION

The present invention relates to apparatus for winding a continuousribbon of plastic interlayer material onto a mandrel to form a pluralityof plies and cutting each ply into one or more individual sheets of apredetermined size and trapezoidal shape from the continuous ribbon ofmaterial. Means is provided for adjusting the circumference at each endof the mandrel so as to ensure flexibility of the mandrel for supportingplastic sheeting to be cut into different sizes and differenttrapezoidal shapes. Thus, the mandrel is adjustable independently ateach end thereof so that the circumference of the mandrel supporting themultiple plies of sheeting along its longer edge or undyed portion issubstantially equal to an integral number of lengths of the longer sideedge of the predetermined trapezoidal shape and the shorter end of themandrel has an adjusted circumference supporting the shorter edge of theplastic sheeting that it an integral number of lengths of the shorterside edge of the predetermined trapezoidal shape to be cut. Thus, thepresent invention provides a single apparatus that is capable of bothadjusting to the shape desired for the individual trapezoidal sheets tobe cut from the continuous ribbon and also to the size of the sheets.

The trapezoidal shape of each piece taken from the continuous ribbon isobtained by cutting along a line parallel to the central shaft on whichthe adjustable mandrel is rotated. When the lengths of the oppositecircumferences of the adjustable mandrel correspond to the lengths ofthe longer and shorter edges of a single length of the trapezoidal pieceto be cut, only one cut parallel to the axis of the central shaft isnecessary. When the opposite circumferences of the mandrel arelengthened to correspond to a plurality of lengths to be cut, two ormore cuts are provided. All of these cuts are made in a directionparallel to the axis of the central shaft of the mandrel. The cut sheetsdevelop a trapezoidal shape because of the conical shape of the outerarms of the doubly adjustable mandrel.

The present invention will be understood better in the light of adescription of a specific embodiment which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings that form part of the description of a specificembodiment of the present invention and where like reference numbersrefer to like structural elements,

FIG. 1 is a transverse view of an illustrative embodiment builtaccording to the present invention;

FIG. 2 is an end view of one of the ends of the mandrel depicted in FIG.1;

FIG. 3 is an end elevational view of a typical adjustment housingforming part of the illustrative embodiment of this invention;

FIG. 4 is a view taken at a right angle to the view of FIG. 3 of saidadjustment housing;

FIG. 5 is an end view of a mandrel adjusting nut that comprises anelement of said illustrative embodiment;

FIG. 6 is a view taken at a right angle to the view of FIG. 5;

FIG. 7 is a cross-sectional view of the center pipe of said embodimentof this invention, showing its relation to said adjustment housing andsaid mandrel adjusting nut;

FIG. 8 is a longitudinal, fragmentary view of said center pipe; and

FIG. 9 is a cross-sectional view taken along the lines 9--9 of FIG. 8showing additional details in phantom.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, the apparatus of the present inventioncomprises a mandrel 10 having a first end member 12 and a second endmember 14. A central pipe 16 interconnects the end members 12 and 14. Aplurality of radially extending arms 18 is attached in equi-angularrelation about end member 12. An equal number of radially extending arms20 is attached in equi-angular relation about end member 14. The radialarms 18 attached to the first end member 12 are aligned with thecorresponding radially arms 20 attached to the second end member 14.Each of the radial arms 18 and 20 is provided with a radially extendinggroove 22. (See FIG. 2) A peripheral arm 24 interconnects each radiallyextending arm 18 and its corresponding radially extending arm 20. Theillustrative embodiment show 8 radial arms 18, 8 radial arms 20 and 8peripheral arms 24. It is understood that the number illustrated isexemplary and may be increased or decreased as desired without departingfrom the gist of this invention. Each peripheral arm has one end portionengaging the groove 22 of one of the radially extending arms 18 and ananother end portion engaging the groove 22 in the corresponding radiallyextending arm 20.

A first adjustment housing 26 is mounted in sliding relation to acentral pipe 16 to the side of the longitudinal center of the pipe 16extending forward the first end member 12. A second adjustment housing28 is mounted in sliding relation to the central pipe 16 to the side ofthe longitudinal center of the pipe 16 extending toward the second endmember 14.

The adjustment housing 26 as seen in FIGS. 3 and 4 comprises a slottedcylindrical member 30 having a pair of diametrically opposed, axiallyextending slots 32 and eight tabs 34 extending radially outward at 45degree intervals from the outer surface of the cylindrical member 30.Each of the tabs 34 has an aperture 36 at its outer portion. Thecylindrical member 30 has an inner circumferential wall sufficient indiameter to clear the outer circumferential wall of the central pipe 16.

A first mandrel adjusting nut 40 (see FIGS. 5 and 6) is received withinthe central pipe 16 as depicted in the cross-sectional view of FIG. 7.The nut 30 comprises an inner cylindrical housing 42 having an outerwall of sufficient dimension to slide within the inner wall of thecentral pipe 16 and a pair of diametrically opposed, radially extendinglugs 44. The inner wall 46 of the inner cylindrical housing 42 isthreaded to mate with a threaded rod 48 that extends within the centralpipe 16 to a threaded connection with the threaded inner wall 46 of theinner cylindrical housing. The threaded rod 48 is connected at its outerend to a first crank means 50.

The first crank means 50 is located adjacent the first end member 12 ofthe mandrel 10. In order to insure that the first adjustment housing 26moves axially when the first crank means is actuated, the central pipe16 has a pair of diametrically opposed, elongated slots 52 that arealigned with the slots 32 so that the radially extending lugs 44 extendthrough the aligned slots and provide means to cause the firstadjustment housing 26 to move axially relative to central pipe 16 inresponse to movement of the first mandrel adjusting nut 40.

A link member 54 pivotally connects each of the apertured tabs 34 to acorresponding apertured tab 56 attached to an end portion 58 of acorresponding peripheral arm 24 adjacent the radially extending arms 18.This construction and arrangement allows the end portions 58 to movefrom the solid line positions depicted in FIG. 1 to the positionsdepicted in phantom in response to the axial movement of said firstadjustment housing 26.

A second crank means 60 is pivotally connected to the second adjustmenthousing 28 in a manner similar to the operative connection between thefirst crank means 50 and the first adjustment housing 26. For ease offabrication, the right hand portion of the central pipe 16 is providedwith diametrically opposed, elongated slots 62 that are 90 degrees outof alignment and spaced longitudinally of slots 52. The secondadjustment housing 28 is provided with tabs 63 attached thereto andarranged in a manner similar to the arrangement of the tabs 34 relativeto the first adjustment housing 26. A series of link members 64pivotally interconnect each of the tabs 63 to a corresponding aperturedtab 66 attached to the end portion 68 of the corresponding peripheralarm 24 adjacent radially extending arms 20.

It is now obvious that the first crank means 50 can be operated toadjust the circumference of the mandrel 10 at its axial end portionadjacent the radially extending arms 18 independently of the operationof the second crank means 60 to adjust the circumference of the mandrel10 at its axial end portion adjacent the radially extending arms 20.Therefore, it is possible with the apparatus of the illustrativeembodiment to adjust the circumferential length of either axial end ofthe mandrel independently of the adjusted circumferential length of saidmandrel at its other axial end.

Indexing means 72 and 74 extend inward from end members 12 and 14 toguide operators to set the positions of the adjustment housings 26 and28 into positions required for any given pattern. Locking means 75 areprovided for each of the crank means 50 and 60 to hold the adjustmenthousings 26 and 28 in their proper locations selected for the pattern tobe produced. When locked, either crank means may be used to wind acontinuous ribbon onto the mandrel.

When a continuous ribbon of plastic interlayer material (such aspolyurethane or plasticized polyvinyl butyral) having a dyed portionalong one longitudinal edge is wound on the mandrel, the opposite axialend portions are adjusted in circumference to correspond with the lengthdesired for an integral number of sheets to be cut from said continuousribbon. This adjustment may be made in advance if the continuous ribbonhas been previously stretched to approximately the differentiallystretched condition desired on an adjustable umbrella-type stretchingcone described and claimed in U.S. Pat. No. 2,933,759 to Startzell,which can be adjusted to provide a desired shape for the boundarybetween the dyed and undyed portions of the ribbon, but is extremelydifficult to obtain a proper circumference corresponding to the lengthrequired along the opposite longitudinal edges of the cut pieces ofinterlayer material.

In cases where the continuous ribbon is wound around the mandrel of thepresent invention in an unstretched condition, the opposite end portionsof the mandrel are independently adjusted in circumference after thecontinuous ribbon of plastic interlayer material is wound on the mandreland the plastic interlayer material is at an elevated temperature atwhich it is readily stretchable. An acceptable temperature range forstretching is 150° F. (65.6° C.) to 190° F. (78.8° C.) with a range of160° F. (71.1° C.) to 170° F. (76.7° C.) preferred. The differentiallyexpanded mandrel with about 30 layers or plies of plastic wound thereonis then kept in its differentially expanded condition for about one hourwhile cooled to room temperature. This is sufficient time for theplastic to set in its differentially stretched state.

Once the plastic is set in its distorted state, it is ready for cutting.An elongated slot 76 is provided in the outward facing surface of one ormore selected peripheral arms 24 to serve as a guide member for acutting knife. A cutting knife is passed along the elongated slot 76 tocut each of the plies. One elongated guide member is used when themandrel is adjusted to opposite circumferential lengths corresponding tothe lengths desired for the dyed edge and undyed edge of each sheet tobe cut from the plies of continuous ribbon.

In order to increase the capacity of the mandrel to cut discrete sheetsof trapezoidal shape from the continuous ribbon, the opposite ends ofthe mandrel may be adjusted to have their circumferences correspond toan integral number of lengths of interlayer sheeting of desired size andof trapezoidal shape. Under such circumstances, if two discrete sheetsof trapezoidal shape are to be cut from each ply of continuous ribbon, apair of peripheral arms 24 in diametrically opposed relation to oneanother are provided with slots 76 for the cutting step. For cuttingthree sheets from each ply, the peripheral arms 24 provided withelongated slots 76 are located around the mandrel in equi-angularrelation 120 degrees apart about its periphery. This latter arrangementwould involve a minimum of six peripheral arms or a multiple of three inexcess of six.

After the sheets are cut from the mandrel, they are stored in horizontalstacks at a controlled temperature (about 70° F. or 21.1° C.) andcontrolled relative humidity (about 20 percent) until such time as theplastic interlayer material is needed. The stored sheets are thenassembled and laminated to glass sheets in the usual manner.

The mandrel 10 may also be used as a stretching means. In order to doso, the mandrel is adjusted so that the circumferences at its oppositeends are equal to one another and correspond to an integral number ofshorter edge lengths desired for the ultimate trapezoidal shapes. Acontinuous ribbon of plastic interlayer material is wound on the mandrelby first clamping an end of the ribbon onto a peripheral arm 24(preferably one provided with a longitudinal slot 76), preferably whilethe ribbon is at an elevated temperture suitable for stretching. The endportion of the mandrel supporting the undyed portion is adjusted toincrease its circumference to correspond to said integral number oflonger edge lengths desired for the ultimate trapezoidal shapes, therebydistorting the plastic plies from cylindrical to conical shapes. Theplastic windings are cooled to room temperature and kept at said coldtemperature until the plastic sets in its distorted shape. The woundplastic is they ready for cutting.

In case the plastic interlayer material is wound on the mandrel while ata temperature below one at which it distorts readily, it becomesnecessary to heat the plastic after it is wound on the mandrel beforeenlarging the circumference of the end of the mandrel that supports theundyed portion. After heating and stretching, the distorted plasticinterlayer material is cooled to set its distorted shape until theplastic interlayer material is ready for cutting.

The mandrel 10 of the present invention has both of its ends adjustableso that its ultimately shorter end can be adjusted to conform to theshorter length of the trapezoidal shape desired while its ultimatelylonger end can be adjusted independently of the adjustment at thesmaller end to provide a circumferential length that corresponds to thelonger length of said trapezoidal shape and also simultaneously controlsthe obliquity of the transverse edges of said trapezoidal shapescompared to their shorter and longer lengths of the longitudinal endedges.

The present invention provides less waste of dyed plastic materialbecause of the ability of the apparatus conforming to the presentinvention to control both the shape and the size of each ply of plasticinterlayer material that is wound on the mandrel. Prior art plasticstretching apparatus did not have the ability to make each ply conformboth in size and shape to an integral number of sheets of variouspatterns cut from a continuous winding of multiple plies of ribbon.

The form of the invention shown and described herein represents apreferred illustrative embodiment thereof. It is understood that variouschanges may be made without departing from the gist of the presentinvention as defined in the claimed subject matter that follows.

I claim:
 1. Apparatus for cutting a series of individual sheet softhermoplastic interlayer material of a preselected trapezoidal shape andof a preselected size from a continuous ribbon of said materialcomprising a mandrel having a first end member and a second end member,a central pipe interconnecting said end members, a plurality of radiallyextending arms attached in equiangular relation about each of said endmembers, the radial arms attached to said first end member being alignedwith corresponding radial arms attached to said second end mbmer, eachof said radial arms having a longitudinally extending groove, aperipheral arm interconnecting each of said radial arms attached to saidfirst end member to said corresponding radial arm attached to saidsecond end member, each peripheral arm having one end portion engagingthe longitudinally extending groove of one of said radial arms attachedto said first end member and another end portion engaging thelongitudinally extending groove of the corresponding one of said radialarms attached to said second end member, a first adjustment housingindepdently mounted to said central pipe for axial movement along oneportion of one side of the center of said central pipe, a secondadjustment housing independently mounted to said central pipe for axialmovement along another portion to the other side of the center of saidcentral pipe, link means interconnecting each of said adjustmenthousings to an adjacent end of each of said peripheral arms, separatecrank means operatively connected independently to each of said abutmenthousings for moving one or the other of said adjustment housingsindependently of one another, whereby the adjusted circumference at eachend of said mandrel is adjustable independently of the adjustedcircumference at the other end of said mandrel so that the mandrel maybe adjusted to receive plies of plastic interlayer material havingdifferent lengths at their opposite longitudinal edges approximatelyequal to an integral number of lengths of the opposite side edges ofsheets of trapezoidal shape to be cut from said continuous ribbon andcan be readily adjustable to accommodate trapezoidal shapes havingdifferent lengths along their opposite longitudinal edges, and meansassociated with said mandrel for cutting said plies along at least oneline in a plane that intersects said central shaft.
 2. Apparatus as inclaim 1, wherein said means associated with said mandrel for cuttingcomprises an elongated groove in an outward facing wall of at least oneof said peripheral arms and a cutting knife having a blade adapted to bereceived in said elongated groove for guidance in movement therealong.